Arg splat experiment - hir FnDecl impl by teor2345 · Pull Request #157699 · rust-lang/rust

teor2345 · 2026-06-10T10:17:44Z

This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals:

I've split it from #153697 to make reviewing easier, see that PR for more details.

The PR is the HIR-level implementation of the feature, excluding typecheck:

Add splat to HIR FnDecl
refactor param_count so it returns a struct, and rename to param_info

Once this PR merges, I'll rebase #153697.

There aren't any extra tests in this PR, because it doesn't have much externally visible functionality. The visible functionality and tests are in the rest of #153697.

rustbot · 2026-06-10T10:17:48Z

HIR ty lowering was modified

cc @fmease

rustbot · 2026-06-10T10:17:50Z

r? @oli-obk

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oli-obk

@bors r+ rollup

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rust-bors · 2026-06-10T11:29:39Z

📌 Commit 746fc13 has been approved by oli-obk

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 5. This pull request will be tested once the tree is reopened.

…uwer Rollup of 14 pull requests Successful merges: - #157280 (traits: Allow escaping self types in ExistentialTraitRef::with_self_ty) - #157282 (Fix post-monomorphization error note race in the parallel frontend) - #157352 (Make the retained dep graph deterministic under the parallel frontend) - #157601 (Emit error for unused target expression in glob and list delegations) - #157626 (Autogenerate unstable compiler flag stubs for unstable-book) - #157647 (Start using comptime for reflection intrinsics and their wrapper functions) - #157013 (Ensure inferred let pattern types are well-formed) - #157288 (platform support: add SNaN erratum to MIPS targets) - #157355 (Add `or_try_*` variants for `HashMap` and `BTreeMap` Entry APIs) - #157577 (Fix parser error recovery treating 'dyn' as a strict keyword in Rust …) - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N)) - #157691 (Move symbol hiding code to a new file) - #157700 (Rename `errors.rs` file to `diagnostics.rs` (5/N)) - #157703 (Fix doc link to Instant sub in saturating caveat) Failed merges: - #157699 (Arg splat experiment - hir FnDecl impl)

Rollup of 23 pull requests Successful merges: - #157280 (traits: Allow escaping self types in ExistentialTraitRef::with_self_ty) - #157282 (Fix post-monomorphization error note race in the parallel frontend) - #157352 (Make the retained dep graph deterministic under the parallel frontend) - #157601 (Emit error for unused target expression in glob and list delegations) - #157611 (Update `browser-ui-test` version to `0.24.0`) - #157620 (Add a strategy FnMut to inject behavior into the flush cycle) - #157645 (Windows TLS - Only register the `atexit` hook when `cleanup` can be unloaded) - #157647 (Start using comptime for reflection intrinsics and their wrapper functions) - #157719 (resolve: Partially revert "Remove a special case for dummy imports") - #156497 (fix-155516: Don't suggest wrong unwrap expect) - #156583 (Support defaults for static EIIs) - #157013 (Ensure inferred let pattern types are well-formed) - #157230 (borrowck: avoid ICE describing fields on generic params) - #157288 (platform support: add SNaN erratum to MIPS targets) - #157350 (compiletest: ignore SVG `y` offset in by-lines comparison) - #157355 (Add `or_try_*` variants for `HashMap` and `BTreeMap` Entry APIs) - #157384 (Add `#[rustc_dump_generics]` attribute) - #157577 (Fix parser error recovery treating 'dyn' as a strict keyword in Rust 2015 when used in `dyn + dyn`) - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N)) - #157691 (Move symbol hiding code to a new file) - #157697 (Add more tests that exercise the well-formedness checking of lazy type aliases) - #157700 (Rename `errors.rs` file to `diagnostics.rs` (5/N)) - #157703 (Fix doc link to Instant sub in saturating caveat) Failed merges: - #157699 (Arg splat experiment - hir FnDecl impl)

Rollup of 31 pull requests Successful merges: - #141030 (Expand free alias types during variance computation) - #154853 (mgca: Register `ConstArgHasType` when normalizing projection consts) - #155527 (Replace printables table with `unicode_data.rs` tables) - #156629 (Stabilize `core::range::{legacy, RangeFull, RangeTo}`) - #157280 (traits: Allow escaping self types in ExistentialTraitRef::with_self_ty) - #157282 (Fix post-monomorphization error note race in the parallel frontend) - #157352 (Make the retained dep graph deterministic under the parallel frontend) - #157601 (Emit error for unused target expression in glob and list delegations) - #157611 (Update `browser-ui-test` version to `0.24.0`) - #157620 (Add a strategy FnMut to inject behavior into the flush cycle) - #157645 (Windows TLS - Only register the `atexit` hook when `cleanup` can be unloaded) - #157646 (Keep rename-imported main alive in dead-code analysis under `--test`) - #157647 (Start using comptime for reflection intrinsics and their wrapper functions) - #157719 (resolve: Partially revert "Remove a special case for dummy imports") - #155153 (Ensure Send/Sync is not implemented for std::env::Vars{,Os}) - #155198 (fix(mgca): Allow specifying generic args (of enum) on enum itself in unit & tuple variant constructions in (direct) const args) - #155323 (refactor `TypeRelativePath::AssocItem` to use `AliasTerm`) - #156497 (fix-155516: Don't suggest wrong unwrap expect) - #156583 (Support defaults for static EIIs) - #157013 (Ensure inferred let pattern types are well-formed) - #157196 (Only suggest reborrowing a moved value where the reborrow is valid) - #157230 (borrowck: avoid ICE describing fields on generic params) - #157288 (platform support: add SNaN erratum to MIPS targets) - #157330 (remove `IsTypeConst` from `hir::TraitItemKind`) - #157350 (compiletest: ignore SVG `y` offset in by-lines comparison) - #157355 (Add `or_try_*` variants for `HashMap` and `BTreeMap` Entry APIs) - #157577 (Fix parser error recovery treating 'dyn' as a strict keyword in Rust 2015 when used in `dyn + dyn`) - #157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N)) - #157691 (Move symbol hiding code to a new file) - #157700 (Rename `errors.rs` file to `diagnostics.rs` (5/N)) - #157703 (Fix doc link to Instant sub in saturating caveat) Failed merges: - #157699 (Arg splat experiment - hir FnDecl impl)

rustbot · 2026-06-11T11:36:06Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

teor2345 · 2026-06-11T11:38:51Z

Just a minor rebase conflict in the param_info refactor

@rustbot reviewer

Rollup of 31 pull requests Successful merges: - rust-lang#141030 (Expand free alias types during variance computation) - rust-lang#154853 (mgca: Register `ConstArgHasType` when normalizing projection consts) - rust-lang#155527 (Replace printables table with `unicode_data.rs` tables) - rust-lang#156629 (Stabilize `core::range::{legacy, RangeFull, RangeTo}`) - rust-lang#157280 (traits: Allow escaping self types in ExistentialTraitRef::with_self_ty) - rust-lang#157282 (Fix post-monomorphization error note race in the parallel frontend) - rust-lang#157352 (Make the retained dep graph deterministic under the parallel frontend) - rust-lang#157601 (Emit error for unused target expression in glob and list delegations) - rust-lang#157611 (Update `browser-ui-test` version to `0.24.0`) - rust-lang#157620 (Add a strategy FnMut to inject behavior into the flush cycle) - rust-lang#157645 (Windows TLS - Only register the `atexit` hook when `cleanup` can be unloaded) - rust-lang#157646 (Keep rename-imported main alive in dead-code analysis under `--test`) - rust-lang#157647 (Start using comptime for reflection intrinsics and their wrapper functions) - rust-lang#157719 (resolve: Partially revert "Remove a special case for dummy imports") - rust-lang#155153 (Ensure Send/Sync is not implemented for std::env::Vars{,Os}) - rust-lang#155198 (fix(mgca): Allow specifying generic args (of enum) on enum itself in unit & tuple variant constructions in (direct) const args) - rust-lang#155323 (refactor `TypeRelativePath::AssocItem` to use `AliasTerm`) - rust-lang#156497 (fix-155516: Don't suggest wrong unwrap expect) - rust-lang#156583 (Support defaults for static EIIs) - rust-lang#157013 (Ensure inferred let pattern types are well-formed) - rust-lang#157196 (Only suggest reborrowing a moved value where the reborrow is valid) - rust-lang#157230 (borrowck: avoid ICE describing fields on generic params) - rust-lang#157288 (platform support: add SNaN erratum to MIPS targets) - rust-lang#157330 (remove `IsTypeConst` from `hir::TraitItemKind`) - rust-lang#157350 (compiletest: ignore SVG `y` offset in by-lines comparison) - rust-lang#157355 (Add `or_try_*` variants for `HashMap` and `BTreeMap` Entry APIs) - rust-lang#157577 (Fix parser error recovery treating 'dyn' as a strict keyword in Rust 2015 when used in `dyn + dyn`) - rust-lang#157670 (Rename `errors.rs` file to `diagnostics.rs` (4/N)) - rust-lang#157691 (Move symbol hiding code to a new file) - rust-lang#157700 (Rename `errors.rs` file to `diagnostics.rs` (5/N)) - rust-lang#157703 (Fix doc link to Instant sub in saturating caveat) Failed merges: - rust-lang#157699 (Arg splat experiment - hir FnDecl impl)

JonathanBrouwer · 2026-06-11T16:43:15Z

@bors r=oli-obk

rust-bors · 2026-06-11T16:43:19Z

📌 Commit d248472 has been approved by oli-obk

It is now in the queue for this repository.

…r=oli-obk Arg splat experiment - hir FnDecl impl This PR is part of the argument splatting lang experiment, and FFI overloading / C++ interop project goals: - rust-lang#153629 - https://rust-lang.github.io/rust-project-goals/2026/overloading-for-ffi.html - https://rust-lang.github.io/rust-project-goals/2025h2/interop-problem-map.html I've split it from rust-lang#153697 to make reviewing easier, see that PR for more details. The PR is the HIR-level implementation of the feature, excluding typecheck: - Add splat to HIR FnDecl - refactor `param_count` so it returns a struct, and rename to `param_info` Once this PR merges, I'll rebase rust-lang#153697. There aren't any extra tests in this PR, because it doesn't have much externally visible functionality. The visible functionality and tests are in the rest of rust-lang#153697.

…uwer Rollup of 23 pull requests Successful merges: - #157716 (update Enzyme, June'26) - #149793 (Add inline asm support for amdgpu) - #152852 (Remove driver_lint_caps) - #155299 (make repr_transparent_non_zst_fields a hard error) - #155439 (Enable Cargo's new build-dir layout) - #157612 (Add a test where subtyping inhibits coercion.) - #157626 (Autogenerate unstable compiler flag stubs for unstable-book) - #157667 (Rename typing modes to better describe real usage) - #156212 (Additionally gate negative bounds behind new `-Zinternal-testing-features`) - #157342 (Reduce verbosity of cycle errors when possible) - #157366 (Add a regression test for an unconstrained TransmuteFrom ICE) - #157459 (rustc_target: callconv: powerpc64: Remove unreachable fallback code path) - #157658 (UnsafeCell: mention shared-ref-to-interior case, fix aliasing model inaccuracy) - #157698 (Remove an unnecessary cloning) - #157699 (Arg splat experiment - hir FnDecl impl) - #157713 (resolve: Remove exported imports from `maybe_unused_trait_imports`) - #157722 (Move create_scope_map to rustc_codegen_ssa.) - #157725 (Keep generic suggestion for macro-expanded missing-type items) - #157733 (Remove old FIXMEs about nocapture attribute) - #157737 (Reorganize `tests/ui/issues` [7/N]) - #157746 (supports_c_variadic_definitions: extend checklist for new targets) - #157763 (Move unused target expression error to appropriate place and rename it) - #157768 (codegen_ssa: peel trans. wrappers on scalable vecs)

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 10, 2026

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teor2345 mentioned this pull request Jun 10, 2026

Add arg splat experiment initial tuple impl #153697

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teor2345 commented Jun 10, 2026

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Comment thread compiler/rustc_ast_passes/src/diagnostics.rs

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Tracking Issue for argument splatting lang experiment #153629

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Rollup of 14 pull requests #157708

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Rollup of 17 pull requests #157720

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Rollup of 23 pull requests #157726

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Rollup of 28 pull requests #157735

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teor2345 added 2 commits June 11, 2026 13:34

Add HIR FnDecl for #[splat]

4abb0aa

Make the param_info return type into a struct, and rename the function

d248472

teor2345 force-pushed the fn-arg-splat-exp-hir-fn branch from 746fc13 to d248472 Compare June 11, 2026 11:36

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JonathanBrouwer mentioned this pull request Jun 11, 2026

Rollup of 23 pull requests #157784

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